Open a New Browser WindowIn the upper right hand corner there is a box with 3 dots - Click thatIn the upper left corner click ExtensionsIn the search box type "Epub" as those are ereader filesThen hit enterIt should bring up a list of extensions and apps you can add to your Chrome browserThe easiest would be to look for Simple Ereader/epubOn the right side of it click Add to ChromeThis should open the Google apps main page

Click the Simple ereader iconClick to add a file (looks like a book)It will let you search for the file you just downloaded. It's probably in your downloadsOnce you find it, click it to open itThe book should appear on your screen

----To use the reader again---Simply open a Google Chrome windowClick Apps (upper left side)Click Simple Epub readerYour book should be listed on the History side to open without needing to search again.